Intermodulation distortion is defined as the production of new output signals which are created from the nonlinear combination of two or more input signals. IMD can be described by examining the linearity of a two-port network.
It's heavily reliant on harmonic distortion (THD - total harmonic distortion plus noise), but not in any easily calculated way. For a 123Hz B fundamental, the amp adds a 246Hz harmonic. Figure 2 - Intermodulation Distortion Waveforms The green trace shows the asymmetrical distortion, while the red trace is symmetrical. The better it is understood, the better its effects can be minimized. We usually describe the frequency spectrum of guitar amp distortion in terms of harmonics. Second-order … Intermodulation distortion (IMD) can wreak havoc in modern wireless-communications systems. IMD (intermodulation Distortion) is one of the main culprits that can make amplifiers sound 'bad'. The input voltage is the same for both, but the peak amplitude is slightly lower with symmetrical distortion because both positive and negative peaks are (soft) clipped equally. This intermodulation occurs because of the nonlinearity in the amplification process. Any amplifier that has harmonicdistortion, has intermodulationdistortion as well, and the converse is also true.

This study of IMD will explore the relationship between the intercept points and the coefficients of the polynomial that is used to model the transfer function of an … If the input of a linear time-invariant system is a signal of a single frequency, then the output is a signal of the same frequency; only the amplitude and phase can differ from the input signal. Depending on the specific carrier frequencies of the transmitted signals, some of these intermodulation products may end up within the device receiver band causing “self-interference,” also referred to as intermodulation distortion (IMD). The order of the intermodulation product depends on how many input signals are mixed and which harmonics of each of those input signals have mixed. The IMD will add to the receiver noise and lead to a degradation of the receiver sensitivity. A linear system cannot produce intermodulation. A single-ended power amp, for example, creates mostly second-harmonic distortion.

Passive intermodulation happens when multiple signal combines in non-linear passive devices like directional coupler, power divider, power splitter, RF isolator, RF circulators, attenuators and adaptors etc… A Fender Champ takes an 82Hz low-E fundamental from the guitar and adds a 6V6-generated second harmonic at 164Hz.